From 6fe6b2d6dabf392aceb3ad3a5e859b46a04465c6 Mon Sep 17 00:00:00 2001 From: Rik van Riel Date: Mon, 7 Oct 2013 11:29:08 +0100 Subject: [PATCH] sched/numa: Do not migrate memory immediately after switching node The load balancer can move tasks between nodes and does not take NUMA locality into account. With automatic NUMA balancing this may result in the tasks working set being migrated to the new node. However, as the fault buffer will still store faults from the old node the schduler may decide to reset the preferred node and migrate the task back resulting in more migrations. The ideal would be that the scheduler did not migrate tasks with a heavy memory footprint but this may result nodes being overloaded. We could also discard the fault information on task migration but this would still cause all the tasks working set to be migrated. This patch simply avoids migrating the memory for a short time after a task is migrated. Signed-off-by: Rik van Riel Signed-off-by: Mel Gorman Cc: Andrea Arcangeli Cc: Johannes Weiner Cc: Srikar Dronamraju Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/r/1381141781-10992-31-git-send-email-mgorman@suse.de Signed-off-by: Ingo Molnar --- kernel/sched/core.c | 2 +- kernel/sched/fair.c | 18 ++++++++++++++++-- mm/mempolicy.c | 12 ++++++++++++ 3 files changed, 29 insertions(+), 3 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 66b878e94554..9060a7f4e9ed 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1631,7 +1631,7 @@ static void __sched_fork(struct task_struct *p) p->node_stamp = 0ULL; p->numa_scan_seq = p->mm ? p->mm->numa_scan_seq : 0; - p->numa_migrate_seq = 0; + p->numa_migrate_seq = 1; p->numa_scan_period = sysctl_numa_balancing_scan_delay; p->numa_preferred_nid = -1; p->numa_work.next = &p->numa_work; diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index b1de7c55e9f7..61ec0d4765b9 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -884,7 +884,7 @@ static unsigned int task_scan_max(struct task_struct *p) * the preferred node but still allow the scheduler to move the task again if * the nodes CPUs are overloaded. */ -unsigned int sysctl_numa_balancing_settle_count __read_mostly = 3; +unsigned int sysctl_numa_balancing_settle_count __read_mostly = 4; static inline int task_faults_idx(int nid, int priv) { @@ -980,7 +980,7 @@ static void task_numa_placement(struct task_struct *p) /* Update the preferred nid and migrate task if possible */ p->numa_preferred_nid = max_nid; - p->numa_migrate_seq = 0; + p->numa_migrate_seq = 1; migrate_task_to(p, preferred_cpu); } } @@ -4121,6 +4121,20 @@ static void move_task(struct task_struct *p, struct lb_env *env) set_task_cpu(p, env->dst_cpu); activate_task(env->dst_rq, p, 0); check_preempt_curr(env->dst_rq, p, 0); +#ifdef CONFIG_NUMA_BALANCING + if (p->numa_preferred_nid != -1) { + int src_nid = cpu_to_node(env->src_cpu); + int dst_nid = cpu_to_node(env->dst_cpu); + + /* + * If the load balancer has moved the task then limit + * migrations from taking place in the short term in + * case this is a short-lived migration. + */ + if (src_nid != dst_nid && dst_nid != p->numa_preferred_nid) + p->numa_migrate_seq = 0; + } +#endif } /* diff --git a/mm/mempolicy.c b/mm/mempolicy.c index aff1f1ed3dc5..196d8da2b657 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -2378,6 +2378,18 @@ int mpol_misplaced(struct page *page, struct vm_area_struct *vma, unsigned long last_nidpid = page_nidpid_xchg_last(page, this_nidpid); if (!nidpid_pid_unset(last_nidpid) && nidpid_to_nid(last_nidpid) != polnid) goto out; + +#ifdef CONFIG_NUMA_BALANCING + /* + * If the scheduler has just moved us away from our + * preferred node, do not bother migrating pages yet. + * This way a short and temporary process migration will + * not cause excessive memory migration. + */ + if (polnid != current->numa_preferred_nid && + !current->numa_migrate_seq) + goto out; +#endif } if (curnid != polnid) -- 2.20.1